Alien mink have for years wreaked havoc on aquatic birdlife and water vole populations across Norfolk.

Increasing numbers of alien mink have for years wreaked havoc on aquatic birdlife and water vole populations across Norfolk.

However, a trapping project started in 2003 to cull their numbers is making headway in the fight against the invasive species.

Norfolk Mink Project coordinator Dr Katy Owen said the organisation was started when “catastrophic” declines in water vole populations were seen.

The American mink is not native to the UK and was originally brought to the country for fur farming.

“A peak was reached in the 1920s when mink fur was very popular,” said Dr Owen. “There were a lot of escapees from mink farms and also intentional releases by animal rights activists.”

She said there was no natural predator of the mink and they soon spread across the country.

Their impact on water vole numbers, which have undergone one of the most serious declines of any native British mammal over the last century, was particularly severe.

They also prey on birds eggs, hatchlings and small fish.

“Many people really only became aware of what a problem they were causing in the early 2000s,” said Dr Owen.

“It is difficult to know just how many there are out there but our trapping is having an effect and numbers are decreasing.”

Figures provided by the project reveal that the number of mink trapped in 2016 in Norfolk was down 33pc from the previous year.

The Bure catchment area saw the most significant reduction, where the number taken was down 55pc from 2015. Projects to eradicate the black ferret-sized carnivores are ongoing in Scotland, Wales and in other areas of England.

Local angling expert Roy Webster said otter were often unfairly criticised for the destruction caused by mink.

“Those of us well into our 80s, born in the Broads area, can recall the years when otters thrived before they became victims of deadly agricultural chemicals in their food chain,” he said.

“Most certainly their predatory activities did not affect the local bird population then for on Hickling Broad one annual coot shoot attended by royalty, downed a bag of 800 birds.”